Video lesson covers a string change from .009 Gauge to .011 Gauge guitar strings. However, the main focus of the lesson is that of checking and setting intonation.

Intonation on a guitar has to do with how "in tune" a string on the instrument is in relationship to the ratio of all of the other notes found on the fingerboard for that particular string. For example, a 3rd string fifth fret "C" note should sound as a "C" note would sound on any other instrument. How "in tune" that "C" note resonates is a reflection of that guitar's intonation on that string. The saddles of most all electric guitar bridge systems are adjustable both forward and backwards. The movement of those saddles adjusts the guitars intonation. The relation of tones on the fingerboard to their key or harmony must be as pure as possible. The video details the process of achieving this.